Method of adding solids and oxygen to an open hearth furnace



R. W. SMITH Feb. 14, 1967 METHOD OF ADDING SOLIDS AND OXYGEN TO AN OPEN HEARTH FURNACE Original Filed July 27, 1961 ng i gif wwm United States Patent METHOD OF ADDING SOLIDS AND OXYGEN TO- This application, which is a division of my co-pending application Serial No. 127,184, filed July 27, 1961, now Patent No. 3,240,481, relates to a method of adding solids and oxygen to an open hearth furnace. The most common way of adding solids to an open hearth furnace is to have the charging machine dump predetermined quantities of material, such as ore and lime, into the furnace during the working period in order to remove excess sulfur, phosphorous, manganese, carbon and silicon. This method of charging takes considerable time and it has therefore been impossible to obtain the maximum production which otherwise would be possible when using oxygen additions to the open hearth furnace. Considerable time is also required for the additions to dissolve into the slag and react with the molten metal. In an attempt to promote faster reaction time, the fines have been introduced into the furnace through a lance with the fines being carried in an oxygen or air stream. However, with those previous lances and methods in which the fines are introduced through a single opening, it has been found that there is too much splashing when the oxygen bearing the fines strikes the bath. On the other hand when the oxygen and fines are introduced through a plurality of small orifices plugging or erosion of the orifices occurs. Also, in order to introduce sufficient oxygen into the furnace the oxygen must travel at speeds between 450 and 750 ft. per second. This increases the erosion of the orifices and also presents possible damage from a physical explosion due to friction at the high speeds.

It is therefore. an object of my invention to provide a method of operating an open hearth furnace in which in which solids and oxygen are introduced simultaneously into the furnace.

This and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a schematic view of an open hearth furnace equipped with the apparatus of my invention;

FIGURE 2 is an enlarged view, partly in section, of the lance of my invention;

FIGURE 3 is a view taken on the line IIIIII of FIGURE 4; and

FIGURE 4 is a view taken on the line IVIV of FIGURE 3.

Referring more particularly to the drawings, reference numeral 2 indicates a steel producing open hearth furnace having a roof 4 and a hearth 6 containing a bath of molten steel and slag 8. Lance 10 extends downwardly through a water cooled donut 12 or other opening in the roof and terminates a shoft distance above the bath. The lance 10 includes concentric tubes 14, 16, 18 and 20 which are connected at their discharge or lower ends by means of a nozzle end 22 welded to the tubes as shown. It will be seen that in addition to the passageway through the inner tube 14 passageways 24, 26 and 28 are provided between the tubes. The nozzle end 22 has an axial opening 30 therethrough of the same internal diameter as tube 14. Six passageways 32 in the nozzle end 22 extend between pasageways 24 and 28. Six openings 34 are provided in the nozzle end 22 between passageways 32 in communication with passageway 26. As

3,304,173 Patented Feb. 14, 1967 shown, the openings 34 extend inwardly and then diverge downwardly away from the axis of the lance. An opening 36 extends inwardly and downwardly from each opening 34 into the opening 30 preferably adjacent the lower end thereof. The upper part of tube 14 extends through a collar and stuffing box 38 to an elbow 40 which is connected to a tube 42. The collar 38 is fastened to the outer end of tube 16, such as by welding, so as to form a fluid tight connection. A similar collar and stuffing box 44 is fastened to the outer end of tube 18 with the tube 16 passing therethrough and a similar stufiing box and collar 46 is fastened to tube 20 with the tube 18 passing therethrough. A water inlet 48 is provided into tube 16 between collars 38 and 44 and an oxygen inlet 50 is provided into tube 18 between collars 44 and 46. A water outlet 52 is provided from tube 20 adjacent the collar 46. One end of flexible supply lines 54, 56, 58 and 60 are connected to one end of conduits 42, 48, 50 and 52, respectively. The other ends of lines 54, 56, 58 and 60 are connected to tubes 62, 64, 66 and 68, respectively. Tube 62 is connected by means of a supply line 70 to a jet liner gun 72 which is supplied with compressed air from line 74. The gun 72 is a standard device manufactured by Engineered Equipment, Inc. of Waterloo, Iowa for mixing air and solids and expelling them under pressure. The jet liner gun 72 travels beneath additive bins 76. A separate bin is provided for each additive, such as ore, lime and fiuorspar. Tube 64 is connected to a cooling water supply, tube 66 to an oxygen supply, and tube 68 to a water drain. The lance 10 may be raised and lowered by means of a motor which drives a cable drum 82 having one end of a cable 84 attached thereto. The cable 84 passes over a sheave 86 with its other end being attached to the top of lance 10 in any suitable manner such as by means of a member 88. When the lance 10 is not being used it is raised to the broken line position shown in FIGURE 1 so that it is not subject to the heat of the furnace. When the lance is ready for operation it is lowered through the donut 12 until its lower end is between approximately 4 and 12 in. above the slag in the furnace. In some instances it may be desirable to introduce the solids in an air stream through one lance and the oxygen through one or more lances adjacent the solid lance.

In operation, oxygen alone may be introduced into the furnace 2 through passageway 26 and openings 34. At this time water is also circulated through passageways 24 and 32 to the front end of the lance with the water returning through passageway 28. When the lance is in its lowered position the oxygen stream creates a dish in the bath 8 so as to expose the slag-metal interface. The jet liner gun 72 is moved to a position beneath the bin 76 having ore therein when it is desired to add ore to the bath and beneath the bin having lime therein when it is desired to add crushed lime to the bath. In adding solids, compressed air is delivered to gun 72 through supply line 74 and, depending upon the setting of the gun, between and 1200 pounds of solids per minute are delivered through the opening 30 into the furnace. Thus the rate of flow of solids can be accurately controlled to deliver the solids into the bath at a maximum rate consistent with the ability of the bath to absorb the added solids. The velocity of the air-borne solid stream through nozzle opening 30 is relatively lowbetween 20 and 200 ft. per second. Oxygen is delivered at the same time through openings 34 at a relatively high velocity-between 450 and 750 ft. per second. The volume of air delivered through opening 30 does not exceed 10% of the amount of oxygen delivered through openings 34. The discharging oxygen sweeps the solids from underneath the lance, thus dispersing them into the bath. At

times, metal or slag may enter opening 30 either due to splashing caused by the violent reaction of the bath as a result of the oxygen blow or by accidentally submerging of the lance into the bath. This metal or slag is quickly burned away with the oxygen emerging into opening 30 through passages 36. Thus the lance is always prepared to supply the additives when required.

While one embodiment of my invention has been shown and described it will 'be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. A method of operating a steel producing open hearth furnace having therein a bath of molten metal and slag on top thereof which comprises delivering gas borne solids from the bottom of a conduit located a maximum of 12 in. above the top of said slag downwardly into said bath at a relatively low velocity, delivering oxygen from the bottom of a conduit located adjacent the gas borne solids a maximum of 12 in. above the top of said slag downwardly into said bath at a relatively high velocity with respect to the velocity of the gas borne solids.

2. A method of operating an open hearth furnace according to claim 1 in which the velocity of the gas borne solids leaving the bottom of the first named conduit is 25 between 20 and 200 ft. per second and the velocity of the oxygen leaving the bottom of the second named conduit is between 450 and 750 ft. per second.

3. A method of operating an open hearth furnace according to claim 1 in which the oxygen is delivered into the bath from a plurality of conduits spaced around the first named conduit, and oxygen from the plurality of conduits is introduced into the lower end of said first named conduit above its outlet.

4. A method of operating an open hearth furnace according to claim 3 in which the velocity of the gas borne solids leaving the bottom of the first named conduit is between 20 and 200 ft. per second and the velocity of the oxygen leaving the bottom of the second named conduit is between 450 and 750 ft. per second.

References Cited by the Examiner UNITED STATES PATENTS 2,988,443 6/1961 Metz 7552 2,991,173 7/1961 Trentini et a1. 7552 3,010,820 11/1961 Gracf et al. 7552 3,112,194 11/1963 De Vries 7552 3,130,252. 4/1964 Metz 26634 3,212,880 10/1965 Rinesch 7552 FOREIGN PATENTS 845,643 8/ 1952 Germany.

BENJAMIN HENKIN, Primary Examiner. 

1. A METHOD OF OPERATING A STEEL PRODUCING OPEN HEARTH FURNACE HAVING THEREIN A BATH OF MOLTEN METAL AND SLAG ON TOP THEREOF WHICH COMPRISES DELIVERING GAS BORNE SOLIDS FROM THE BOTTOM OF A CONDUIT LOCATED A MAXIMUM OF 12 IN. ABOVE THE TOP OF SAID SLAG DOWNWARDLY INTO SAID BATH AT A RELATIVELY LOW VELOCITY, DELIVERING OXYGEN FROM THE BOTTOM OF A CONDUIT LOCATED ADJACENT THE GAS BORNE SOLIDS A MAXIMUM OF 12 IN. ABOVE THE TOP OF SAID SLAG 